This invention relates to a semiconductor integrated circuit device, and more particularly to a device capable of exhibiting different functions by the same semiconductor chip.
In general, in semiconductor integrated circuit devices, there are instances where non-connection (NC) terminals which are not connected to the circuit exist in the semiconductor chip. In such case, with a view to adding a new function or functions to semiconductor integrated circuits through the implementation of semiconductor integrated circuits of a multi-functional structure, there have been many occasions where NC terminals are used as terminals for inputting external signals.
In such cases in order not to bring on lowering of productivity, even in cases where a new function is added, it is necessary to maintain the fundamental function conventionally given as it is, to thus ensure compatibility. In the case where a NC terminal is used as the electrode for inputting an external signal and the internal circuit is not used, if that NC terminal is brought into a floating state, there is the possibility that an erroneous operation of the internal circuit may take place. Accordingly, it is required to hold the NC terminal at a positive or negative power supply potential.
For this reason, in conventional devices, in the case where an internal circuit is formed with a view to adding a new function in the semiconductor chip of the package, when this internal circuit is used, a lead for inputting an external signal is connected to an electrode drawn out from the internal circuit for the purpose of inputting an external signal In this case, when this internal circuit is not used, it is necessary to connect that external signal input electrode to a power supply terminal provided outside the chip so that a potential on the external signal input electrode is not placed in a floating state. Accordingly, it is necessary that the electrode be provided at a position close to the power supply terminal. For this reason, internal wiring is required.
However, since a semiconductor manufacturing mask is required in order to form such an internal wiring, two kinds of masks must be prepared for the case where the internal circuit is made operative and the case where the internal circuit is not made operative. Thus, there results increased cost and lowered productive efficiency.
Further, it is conceivable to take measures to connect the internal circuit and one external signal input electrode to further connect the external signal input terminal and an external signal input lead, or to connect the external signal input electrode and a power supply lead. However, in this case, it is required that the external signal input lead and the power supply lead be adjacent to each other, and that the external signal input electrode be provided in the vicinity of these leads. This results in the problem that the circuit design and the chip layout design are greatly restricted.